Actress Sophie Nyweide Dead at 24

9:57 AM PT -- Shelly, Sophie Nyweide’s mom, tells TMZ … “We are very distraught and mourning. All I can say is her time acting was brief but very happy. She wasn't a child star in the least and wasn't subjected to anything hurtful on those films. She was always safe on those sets. Please let her rest in peace now.

"My knowledge is she was using drugs and was a tiny young woman. She was with other people when she died. I didn't know them. There is an investigation ongoing. The autopsy results are not in. They said it would take 6-8 weeks. So I can't say definitively.”

Actress Sophie Nyweide -- famous for her roles in "Mammoth" and "An Invisible Sign" -- is dead.

Sophie died April 14 in Bennington, VT ... according to her family. The cause of death is unclear.

In an obituary, Sophie's family hints at what led to her early death, saying ... "Sophie was a kind and trusting girl. Often this left her open to being taken advantage of by others. She wrote and drew voraciously, and much of this art depicts the depth she had, and it also represents the pain she suffered. Many of her writings and artwork are roadmaps of her struggles and traumas."

They continue ... "Even with those roadmaps, diagnoses and her own revelations, those closest to her, plus therapists, law enforcement officers and others who tried to help her, are heartbroken their efforts couldn't save her from her fate. She self-medicated to deal with all the trauma and shame she held inside, and it resulted in her death. She repeatedly said she would 'handle it' on her own and was compelled to reject the treatment that might possibly have saved her life."

Sophie appeared in 7 films before her 11th birthday ... including "Noah," "Bella," "Margot at the Wedding," and "Shadows & Lies." She also had gigs on TV shows like "Law & Order" and "What Would You Do?"

Her family is remembering her as "creative, athletic and wise beyond her years ... She dreamed (more like demanded!) to be an actor, without ever knowing her mother was an actor, so she did that too with an ease we all marveled about. She seemed happiest on a movie set, becoming someone else."

Sophie was 24.